In young and elderly, this study will 1) determine the relationship between postural control and attentional resource allocation; 2) investigate the dynamics of attentional and postural control during balance recovery and 3) investigate the effect of increasing attentional resource allocation on postural control during balance recovery. Within three experiments, postural stability, attentional resource allocation, and their interaction will be measured under conditions of varying postural challenge in both young and elderly populations. Postural challenge will be varied through support surface and or visual scene manipulations. Attentional resource allocation will be probed by having subjects perform attentional tasks (simple reaction time and inhibition reaction time tasks) concurrent with assessment of postural stability during 5 different postural tasks. The results of this project will lead to a better understanding of the relation between attention and postural control that will better explain the decline in balance and increase in falls in the elderly and suggest new strategies to prevent falls.